Atomising nozzle

ABSTRACT

An atomizer nozzle ( 1 ) for fuels, in particular for feeding them into a chemical reformer for obtaining hydrogen, has a nozzle body ( 2 ) containing spray-discharge orifices ( 3 ) that discharge into a metering space, and has at least one metering aperture ( 6 ). The spray-discharge orifices ( 3 ) are situated at elevation levels ( 4 ) so as to have a radial directional component with respect to a center line ( 10 ) of the nozzle body ( 2 ), each elevation step having at least one spray-discharge orifice ( 3 ), and the spray-discharge orifices ( 3 ) of at least one elevation level ( 4 ) being connected to at least one channel ( 14 ) of a nozzle-body insert ( 5 ) that has at least one flow-through opening ( 11 ).

BACKGROUND INFORMATION

In fuel-cell-supported transportation systems, so-called chemicalreformers are used for extracting the required hydrogen fromhydrocarbon-containing fuels.

All the substances needed by the reformer for the course of reaction,such as air, water, and fuel, are ideally supplied to the reformer inthe gaseous state. However, since the fuels, such as methanol orgasoline, and water are preferably present onboard the transportationsystem in liquid form, they must be heated shortly before being suppliedto the reformer, in order to vaporize them. This requires apre-evaporator capable of providing adequate quantities of gaseous fueland water vapor, the waste heat of the reformer mostly being used forvaporization.

Since the hydrogen is normally consumed immediately, chemical reformersmust be capable of adjusting the production of hydrogen to the demandwithout delay, e.g. in response to load changes or during start phases.Especially in the cold start phase, additional measures must be taken,since the reformer does not provide any waste heat. Conventionalevaporators are not capable of generating adequate quantities of gaseousreactants without delay.

So-called catalytic burners provide the temperature required for thechemical reaction, in which, e.g. the fuel is reformed to form, amongother things, hydrogen. Catalytic burners are components that havesurfaces coated with a catalyst. In these catalytic burners, thefuel/air mixture is converted into heat and exhaust gases, the generatedheat being conducted to the suitable components such as the chemicalreformer or an evaporator via, for example, the (lateral) surfacesand/or via the warm exhaust-gas stream.

The conversion of fuel into heat is highly dependent on the size of thefuel droplets striking the catalytic layer. The smaller the size of thedroplets and the more uniformly the catalytic layer is wetted with thefuel droplets, the more completely the fuel is converted into heat andthe higher the efficiency. In this way, the fuel is also converted morequickly and pollutant emissions are reduced. Fuel droplets that are toolarge in size result in the coating of the catalytic layer and hence, ina slow conversion rate. This leads to, e.g. poor efficiency, especiallyin the cold start phase.

It is therefore practical to introduce the fuel into thereformer/catalytic burner in a finely dispersed form, with the aid of anatomization device, in which case, provided that there is a sufficientsupply of heat, the vaporization process is improved by the high surfacearea of the finely dispersed fuel.

Devices for metering fuels into reformers are known, for example, fromU.S. Pat. No. 3,971,847. According to this document, metering deviceslocated relatively far away from the reformer are used to meter the fuelvia long supply lines and a simple nozzle into a temperature-adjustedmaterial stream. In the process, the fuel first strikes baffle platespositioned downstream from the nozzle outlet orifice, which are designedto swirl and disperse the fuel before arriving, via a relatively longvaporization section (path) necessary for the vaporization process, atthe reaction region of the reformer. The long supply line allows themetering device to be insulated from thermal influences of the reformer.

A particularly disadvantageous feature in the devices known from theabove-mentioned document is the fact that, due to the simpleconstruction of the nozzle and the positioning of the baffle plates, atargeted metering of fuel, for example into regions of the reformer thathave a large supply of heat, is possible only to an insufficient degree.This leads to the need for a relatively large space due to the necessityof a long and voluminous vaporization section.

Furthermore, problems arise in cold start operation, since long andvoluminous vaporization sections are slow to heat up and also give off arelatively large amount of heat unused. The set-ups of nozzle and baffleplates described in U.S. Pat. No. 3,971,847 particularly do not allowthe interior surface of a hollow cylinder to be uniformly wetted withfuel and, in so doing, do not allow certain surfaces of the hollowcylinder to be excluded from being wetted with fuel, or the quantity ofthe metered fuel to be adjusted to the distribution of the supply ofheat in the metering space. Even the shape of the fuel cloud resultingfrom the metering process can be influenced only to an insufficientdegree.

A further disadvantage is that the shape of the fuel cloud or thedistribution of the dosed-in fuel may not be adequately controlled byadjusting the baffle plates.

SUMMARY OF THE INVENTION

The atomizer nozzle according to the present invention has the advantagethat the fuel may be introduced in accordance with the supply of heatprevailing in the metering space. This optimizes the process ofvaporizing the fuel and allows it to take place in a small, rapidlyheated space. In addition, it is possible to improve the operatingperformance, since, for example, measuring paths or measuring surfaces,sensors for instance, may be largely excluded from being acted upon byfuel. The geometry of the discharged fuel or fuel cloud is singularlyadaptable to the circumstances prevailing in the metering space and tothe conditions given thereby.

In particular, the modular construction of the atomizer nozzle allowsthe shape of the fuel cloud and the respective amounts of fuel therebyinjected to be changed rapidly and easily, in order to optimize theatomization operation. This allows considerable cost reductions inadapting to the specific metering space and the conditions prevailing init.

In a first advantageous refinement, the nozzle body of the atomizernozzle is formed as a hollow cylinder. This allows the atomizer nozzleto be manufactured very easily, precisely, and therefore inexpensively.Moreover, the atomizer nozzle may thus be manufactured, for example,from standardized semi-finished parts, e.g. from standardized metaltubes.

In addition, it is advantageous when the nozzle body is completely orpartially made of nozzle-body inserts. In this manner, e.g. the overalllength of the atomizer nozzle may be changed and adapted to therequirements very flexibly, simply, rapidly, and with the use of only afew simple tools. In particular, this allows the atomization operationto be optimized in a rapid and step-by-step manner, for example, in atest phase or development phase. In particular, the number ofspray-discharge orifices of an elevation level and the spacings of theelevation levels may also be changed very rapidly and cost-effectivelyby exchanging nozzle-body inserts.

In addition, it is advantageous to provide the nozzle-body inserts withinternal threads or external threads on the influx and/or discharge end,by which they may be screwed to the nozzle body and/or to anothernozzle-body insert, so as to be hydraulically sealed. In this manner,the nozzle-body inserts may be assembled and disassembled in aparticularly simple, easy, and reliable manner. Furthermore, thenozzle-body inserts may be advantageously press-fitted, bonded, and/orwelded, in particular laser-welded, to the nozzle body in ahydraulically sealed manner, which means that the jointing method may bemore effectively adapted to the environmental conditions andrequirements.

In a further advantageous refinement, a gas-supply port for supplying agas, for example air or residual gases from a fuel-cell process orreforming process, is situated between the spray-discharge orifices ofthe first elevation level and the metering aperture. This allows thepreparation (conditioning) of the mixture to be advantageouslyinfluenced.

Moreover, the atomizer nozzle may be refined in that at least oneadditional spray-discharge orifice is situated downstream from the lastspray-discharge orifice of an elevation level in the direction of thefuel flow, the additional spray-discharge orifice having an axialcomponent with respect to the center line of the nozzle body. Thisallows the atomization of fuel to be adapted even more effectively tothe conditions prevailing in the metering space.

Moreover, the shape of the flow-through opening of the nozzle-bodyinserts may influence the flow behavior or the pressure conditions(compression ratios) in the nozzle body. In this regard, flow-throughopenings having a trapezoidal, a rectangular, or a combination of arectangular and a trapezoidal cross section are particularlyadvantageous, especially since they can be manufactured simply,precisely, and thus inexpensively. It is furthermore advantageous toimplement the flow-through opening in multiple uniform cross sections ofvarying size, for example as a stepped bore hole.

If the nozzle body includes sections of reduced wall thickness, thenparticularly the thermal conductivity in the direction of the meteringpoint will be reduced. Thus, a metering device situated in that locationis protected from excessive heating. The sections of reduced wallthickness may also influence the spray-off (radiation) geometry if theyare situated in the region of the spray-discharge orifices. If thenozzle body is formed by the nozzle-body inserts, then the wallthicknesses of individual nozzle-body inserts may be reduced insections, with the same effects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic sectional view of an exemplary embodiment of anatomization nozzle according to the present invention.

FIG. 2 shows a schematic representation of a first specific embodimentof a nozzle-body insert.

FIG. 3 shows a schematic representation of a second specific embodimentof a nozzle-body insert.

DETAILED DESCRIPTION

The exemplary embodiments described below of atomizer nozzles designedaccording to the present invention allow for simple metering andatomization in a hot atmosphere, while providing a robust, flexible, andtherefore more cost-effective construction, and allow for application indifferent spatial constellations and the use of standard low-pressurefuel injectors.

Identical parts are provided with the same reference numerals in all ofthe figures. The arrows represent the respective fuel and gas flows.

An exemplary embodiment, schematically represented in FIG. 1, of anatomizer nozzle 1 according to the present invention is in the form ofan atomizer nozzle 1 for the use of low-pressure fuel injectors 16.Atomization nozzle 1 is particularly suitable for feeding and atomizingfuel into a metering space (not shown) of a chemical reformer (notshown) for obtaining hydrogen.

In this exemplary embodiment, atomizer nozzle 1 of the present inventionhas a nozzle body 2 in the shape of a hollow cylinder, having a meteringaperture 6 at the top centrally situated with respect to a center line10 of nozzle body 2. This is followed, in the direction of fuel flow 8,by a gas supply port 7 situated on the side wall of nozzle body 2, byeight elevation levels 4, each having a spray-discharge orifice 3situated at a right angle to center line 10 of nozzle body 2, andfinally by the end of nozzle body 2 opposite to metering aperture 6 andhaving a spray-discharge orifice 3.

In this exemplary embodiment, a nozzle-body insert 5 having a coaxialflow-through opening 11 is positioned in nozzle body 2 on the level offirst elevation level 4.1, second elevation level 4.2, fifth elevationlevel 4.5, and seventh elevation level 4.7. Gaps 19 are located betweennozzle-body inserts 5 and between nozzle-body insert 5 situated at thelevel of seventh elevation level 4.7, and the end of nozzle body 2opposite to metering aperture 6. The gaps may also be absent from otherexemplary embodiments. In this exemplary embodiment, center lines 12 offlow-through openings 11 coincide with center line 10 of nozzle body 2.

Nozzle-body inserts 5 are disk-shaped and have channels 14; in thisexemplary embodiment, one channel 14 connecting flow-through opening 11to, in each instance, only one spray-discharge orifice 3. In thisexemplary embodiment, channels 14 take the form of bore holes. At theircircumference, nozzle-body inserts 5 are sealingly joined to nozzle body2 in such a manner, that no fuel or gas may penetrate between nozzlebody 2 and the circumference of nozzle body insert 5. In this exemplaryembodiment, nozzle-body inserts 5 are forced into nozzle body 2. Theymay also be welded or screwed into nozzle body 2. In addition, they maybe attached to other nozzle-body inserts 5 in a hydraulically sealedmanner, via influx-side or discharge-side external threads 18 orinternal threads 17, they then being fit into nozzle body 2 in such amanner, that only negligible amounts of gas and/or fuel can penetratebetween nozzle body 2 and nozzle-body insert 5.

Flow-through openings 11 of nozzle-body inserts 5 take the form of abore having a rectangular cross-section. The shape of nozzle-bodyinserts 4, their fitting position, and the shape or the combination ofshapes of flow-through openings 11 may be arbitrarily combined andvaried for controlling the fuel flow, gas flow, and pressure conditions.The diameter and the shape of the cross-section of channels 14 may bevaried, as well.

The fuel is metered via metering aperture 6, in this exemplaryembodiment via a low-pressure fuel injector 16, into atomizer nozzle 1,i.e. nozzle body 2, and then flows in direction of fuel flow 8 alongcenter line 10 of nozzle body 2, past gas-supply port 7, through whichresidual gases and/or air are fed into nozzle body 2 via a gas pipe 15,to nozzle body insert 5 situated at first elevation level 4.1, where thefuel or the fuel/gas mixture passes through flow-through opening 11. Inthis context, a part of the fuel is distributed to channels 14 anddirected to spray-discharge orifices 3, at which the fuel or thefuel/gas mixture is discharged into the metering space not shown.

On the discharge end, the remaining part of the fuel or fuel/gas mixturenot distributed to channels 14 exits flow-through opening 11 and flowsinto space 19 situated downstream from it in fuel-flow direction 8. Inan analogous manner, the remaining fuel or fuel/gas mixture isdistributed, in each instance, through nozzle-body inserts 5 situateddownstream from it in fuel-flow direction 8. On third elevation level4.3, fourth elevation level 4.4, sixth elevation level 4.6, and eighthelevation level 4.8, which have no nozzle-body inserts 5, the specificportion of fuel or fuel/gas mixture directly enters respectivespray-discharge orifices 3 from space 19 and is discharged into themetering space not shown.

FIG. 2 shows a first specific embodiment of a nozzle-body insert 5. Inthis exemplary embodiment, flow-through opening 11 has, on the influxend, an expanded inner diameter 20 containing internal threads 17 and iscoaxially situated in nozzle-body insert 5.

According to the present invention, nozzle-body insert 5 may be situatedin nozzle body 2 or even constitute nozzle body 2 completely orpartially.

If nozzle-body insert 5 is situated in nozzle body 2 shown in FIG. 1,its structure is as follows:

Channel 14 of nozzle-body insert 5 is formed by bores 21 running on aline perpendicular to center line 12 and by a trapezoidal indentation 22of the outer diameter of nozzle-body insert 5 running radially aroundcenter line 12 of flow-through opening 11. Bore 21 and indentation 22each form a part of channel 14.

A portion of the fuel or the fuel/gas mixture flows from flow-throughopening 11 through bores 21 and indentation 22, in order to be injectedthrough unshown spray-discharge orifices 3 of nozzle body 2 shown inFIG. 1, into the metering space not shown.

If nozzle body 2 is formed by the at least one nozzle-body insert 5, itsstructure is as follows:

Bores 21 running on a line, perpendicularly to center line 12 offlow-through opening 11, form channels 14 and spray orifices 3.Trapezoidal indentation 22 of the outer diameter of nozzle-body insert5, running radially around center line 12 of flow-through opening 11,forms a section 13 of reduced wall thickness, which is used, forexample, for heat insulation.

A portion of the fuel or fuel/gas mixture flows from flow-throughopening 11, through channel 14 taking the form of bores 21, in order tobe injected, at the end of the same bore 21 forming spray-discharge aswell, into the metering space not shown.

FIG. 3 shows a second specific embodiment of a nozzle-body insert 5substantially similar to the first specific embodiment. In contrast tothe specific embodiment represented in FIG. 2, nozzle-body insert 5 hasa somewhat longer axial profile and outer threads 18 situated on thedischarge side. Outer threads 18 are situated on the discharge-side endof nozzle-body insert 5, the outer diameter of the discharge-side endbeing reduced.

The present invention is not limited to the exemplary embodimentsdescribed but is applicable to any other atomization systems.

1. An atomizer nozzle for a fuel, comprising: a modular system of anozzle body formed as a hollow cylinder and at least one disk-shapednozzle body insert; the nozzle body having spray-discharge orifices thatdischarge into a metering space, and having at least one meteringaperture, the spray-discharge orifices being situated at elevationlevels so as to have a radial directional component with respect to acenter line of the nozzle body, each elevation level having at least oneof the spray-discharge orifices, and the at least one spray-dischargeorifice of at least one elevation level being directly connected to atleast one channel of the at least one disk-shaped nozzle-body insertthat has at least one flow-through opening; and wherein the at least onedisk-shaped nozzle body insert has an indentation on its outer diameterforming a section of reduced wall thickness.
 2. The atomizer nozzleaccording to claim 1, wherein the atomizer nozzle is for feeding fuelsinto a chemical reformer for obtaining hydrogen.
 3. The atomizer nozzleaccording to claim 1, wherein the at least one disk-shaped nozzle-bodyinsert includes a plurality of disk-shaped nozzle-body inserts havingone of (a) internal threads and (b) external threads on at least one ofan influx and a discharge side, the disk-shaped nozzle-body insertsbeing screwed to at least one of (a) the nozzle body and (b) anotherdisk-shaped nozzle-body insert in a hydraulically sealed manner with theaid of the one of (a) the internal threads and (b) the external threads.4. The atomizer nozzle according to claim 1, wherein the at least onedisk-shaped nozzle-body insert is at least one of press-fitted, bonded,welded, and laser-welded, to the nozzle body in a hydraulically sealedmanner.
 5. The atomizer nozzle according to claim 1, wherein at leastone additional spray-discharge orifice having an axial directionalcomponent with respect to the center line of the nozzle body is situateddownstream from a last of the elevation levels.
 6. The atomizer nozzleaccording to claim 1, wherein a center line of the flow-through openingof the at least one disk-shaped nozzle-body insert runs parallel to thecenter line of the nozzle body.
 7. The atomizer nozzle according toclaim 1, wherein a cross-section of the flow-through opening is one ofrectangular and trapezoidal.
 8. The atomizer nozzle according to claim1, wherein the flow-through opening has at least two uniformcross-sections of different size, in the form of a stepped bore hole. 9.The atomizer nozzle according to claim 1, wherein the at least onedisk-shaped nozzle body insert has the section of reduced wall thicknessin its axial profile.
 10. The atomizer nozzle according to claim 9,wherein the section of reduced wall thickness runs in a region of the atleast one elevation level.
 11. An atomizer nozzle for a fuel,comprising: a nozzle body having spray-discharge orifices that dischargeinto a metering space, and having at least one metering aperture, thespray-discharge orifices being situated at elevation levels so as tohave a radial directional component with respect to a center line of thenozzle body, each elevation level having at least one of thespray-discharge orifices, and the at least one spray-discharge orificeof at least one elevation level being directly connected to at least onechannel of at least one nozzle-body insert that has at least oneflow-through opening further comprising a gas-supply port situated inthe nozzle body between a first of the elevation levels and the at leastone metering aperture.